1. Field of the Invention
This invention relates generally to a sensing system including a single sensor element and multiple sensor outputs and, more particularly, to a sensing system in a vehicle that employs a single sensor element and multiple sensor outputs, where the system uses the multiple outputs for diagnostic purposes.
2. Discussion of the Related Art
Sensing systems are employed in vehicles for sensing the condition, position, performance, etc. of certain vehicle systems and devices. For example, sensing systems are used for sensing throttle plate position in an electronic throttle body of a vehicle. When an operator of the vehicle presses the accelerator pedal, the accelerator pedal position is detected. The throttle plate position is sensed by a sensing system that provides an output signal to the engine controller of the position. The engine controller provides the proper amount of fuel and air to operate the engine at the desired speed.
Sensor systems of this type can employ two sensor elements for redundancy purposes. The two sensor elements provide two separate sensor output signals to the engine controller. The two output signals are typically different relative to each other, such as having reversed slopes, truncated slopes, etc., so that the two output signals change differently under normal conditions during the sensing operation. The engine controller compares the two output signals to make a determination as to whether the sensors and associated circuitry are operating properly. If one of the sensors fails, or sensor circuitry fails, or sensor connections fail, the corresponding output signal will go out of its normal operating range relative to the other sensor output signal or into a diagnostic range. For example, if a change in the supply voltage to one of the sensor elements changes, its output signal will behave differently than if the supply voltage was unaffected. By comparing the two sensor output signals, the engine controller will thus know if the sensing system is operating properly.
Each sensor element and its associated circuitry are typically provided in a separate circuit, where redundant sensors require two separate chips. This adds additional cost to the system because of the cost of the circuits. It would be desirable to provide two sensor output signals from a sensing system of this type for sensing system diagnostic purposes, yet only have a single sensor element and its associated circuitry on a single chip.